As numbers of computers, particularly servers, are deployed in large-scale or hyper-scale data center applications, the need to connect those computers to one another at massive scale as well as connecting them to the outside world has driven change in data center networking topologies and strategies. Two of the primary drivers of cost and performance in these large networks are the network topology and the photonic interconnections between them. The trend has been to utilize many low-cost low-radix switches connected to other low-radix switches via multiple copper and optical connections. As the networks increase efficiency by increasing data rate, the distances that data signals can traverse in copper cables diminishes as a result of signal integrity loss in the copper medium. Therefore, the ratio of copper to optical cables has trended in favor of optical cables, as the signal traverse distance for optical cables is significantly longer.
The fundamental problem with optical cables is cost. Present optical solutions, which are cost-effective solutions when used to traverse long distances, become inefficient when used to traverse shorter distances. As a result, cost-reduction exercises have developed high-channel-count solutions that amortize the cost of cable attachment and packaging across a larger number of connections. Where current solutions may use optical engines with 4 channels or perhaps 8 channels, these high-density solutions favor 24-36 channels.
The remaining problem is the classical last-mile problem, or in this case, a last-meter problem. Taking 24-channel or 36-channel cables directly to computer servers is not efficient due to over-provisioning. Likewise, taking 4-channel solutions to many servers is not efficient due to duplicative packaging costs. As more networks seek to use high-radix switches in order to remove layers from the network hierarchy, they are challenged by the costs of the final layer connection to the servers. Since the connection between a high-radix middle-of-row switch and a large array of servers requires making many connections, and the array of servers are typically in different equipment racks, the problem of requiring the distance capabilities of optical connections is conflated with the problem of requiring low-cost connections to many servers.
Therefore, there is a need to minimize wired copper connections to servers to allow for longer data transmission lengths provided by fiber optical connections, while also minimizing costly optical fiber connections. Further, legacy servers' output electrical signals and it is desirable to provide a cost-effective system that continues to provide the ability to use legacy server equipment.